\documentclass[a4paper]{article}

\usepackage{probsoln}
\usepackage{graphicx}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{epstopdf}
\usepackage{enumerate}

\showanswers
\newboolean{eachProblemInOnePage}
\setboolean{eachProblemInOnePage}{true}
\newboolean{identifyAuthor}
\setboolean{identifyAuthor}{true}

\begin{document}

	\input{lay_1_3_1.tex}

\end{document}